1. Field of the Invention
The invention relates, generally, to an anti-backlash gear and more specifically, to anti-backlash gears for industrial machinery such as printing presses.
2. Description of the Related Art
Anti-backlash gearing is commonly used in gear trains of instruments and in mechanical computing devices. Gears of this type are well known and are sold in numerous instrument related catalogues. However, these classes of anti-backlash gears are not useful in power transmissions of high speed machinery.
High performance, high horsepower, servo motors used in printing presses create a requirement for gearing that can apply both accelerating and decelerating torque without introducing a following positional error such as would be introduced by normal gear backlash. The gear teeth that mesh between a first gear and a corresponding second gear, such as between a driving gear and a driven gear of a gear train, have a tendency to separate circumferentially when the gears rotate at very high speeds and have backlash problems when torque values are changed on the drive gear.
U.S. Pat. No. 5,813,335 to Burke et al. (Burke) exemplifies the prior art developments to eliminate the backlash problem. Burke teaches a drive gear and a supplemental gear. The supplemental gear has a recess formed therein for housing a leaf spring assembly. The leaf spring assembly biases the teeth of the supplemental gear to rotate opposite the teeth of the drive gear in order to prevent backlash with the teeth of a driven gear. However, the supplemental gear has to be of a minimum size (diameter) in order to house the leaf spring and the leaf springs for developing the anti-backlash forces are short in length and therefore have a high spring rate which is undesirable. In addition, the complexity of the accuracy requirements of the configuration leads to high production costs.